Parameterization of the Angular Distribution of Gamma Rays Produced by p-p Interaction in Astronomical Environment

TL;DR

This paper provides parameterized formulas for the angular distribution of gamma rays from proton-proton interactions, derived from advanced Monte Carlo simulations, to aid astrophysical gamma-ray spectrum calculations considering viewing angles.

Contribution

It introduces new parameterized formulas based on updated proton-proton interaction models, including resonance contributions, for accurate gamma-ray angular distribution predictions in astrophysics.

Findings

Gamma-ray spectra depend on viewing angle.

Formulas accurately reproduce Monte Carlo simulation results.

Application demonstrated for different proton source geometries.

Abstract

We present the angular distribution of gamma rays produced by proton-proton interactions in parameterized formulae to facilitate calculations in astrophysical environments. The parameterization is derived from Monte Carlo simulations of the up-to-date proton-proton interaction model by Kamae et al. (2005) and its extension by Kamae et al. (2006). This model includes the logarithmically rising inelastic cross section, the diffraction dissociation process and Feynman scaling violation. The extension adds two baryon resonance contributions: one representing the Delta(1232) and the other representing multiple resonances around 1600 MeV/c^2. We demonstrate the use of the formulae by calculating the predicted gamma-ray spectrum for two different cases: the first is a pencil beam of protons following a power law and the second is a fanned proton jet with a Gaussian intensity profile impinging on the surrounding material. In both cases we find that the predicted gamma-ray spectrum to be dependent on the viewing angle.